If options does not include the Ordinal value, this overload performs a culture-sensitive search; that is, if the char is a Unicode value representing a precomposed character, such as the ligature 'Æ' (U+00C6), it might be considered equivalent to any occurrence of its components in the correct sequence, such as "AE" (U+0041, U+0045), depending on the culture. If options includes the Ordinal value, this overload performs an ordinal (culture-insensitive) search; that is, a char is considered equivalent to another char only if the Unicode values are the same. Overloads of String.IndexOf that search for a char perform an ordinal search, while those that search for a string perform a culture-sensitive search.